The investigators will in this project make a clinical trial by a randomly selected group of approximately 350 persons in the period 2006-2011, have had RYGB in the Central Region of Denmark. From a medical interview, blood tests, etc. the investigators will be able to give a good estimate of the incidence of medical complications. The investigators will explore complications such as: anemia, hypoglycemia, peripheral nerve problems (especially neuropathies), vitamin D / osteoporosis and other mineral / vitamin deficiencies that may be identified through blood tests.